1. Field of the Invention
The present invention relates to a stator coil assembly, and more particularly, to a stator coil assembly used for an axial-gap rotary electrical machine.
2. Description of the Related Art
Conventionally, regarding the stator coils of an axial-gap rotary electrical machine (an electric motor and an electric generator), there are known technologies of increasing the thickness of a conductor and of stacking the conductors in order to obtain a high torque by allowing a large current to flow therethrough.
Among such stator coils, there is a stator coil (see, for example, JP 2009-183072 A (FIG. 1, and paragraph [0003]) that cools a conductor by attaching a heat-transfer member to the surface of the conductor via an insulating sheet and by transferring heat to a cooling device provided at the inner circumference of a coil in order to prevent the conductor from producing heat by allowing a large current to flow therethrough.
Also, in order to improve the cooling performance, there is a stator coil (see, for example, JP 2008-61375 A (FIG. 6)) having cooling structures like water jackets provided at the both sides of a coil member.
However, according to the conventional stator coils, it is necessary to increase the thickness of the conductor and to stack conductors in a multilayer configuration, which result in the reduction of the heat-transfer efficiency in the thickness direction of the conductor (the axial direction of the rotary electrical machine), so that it becomes difficult to ensure a requisite heat radiation if it is attempted to obtain a high output by allowing a large current to flow through (see FIG. 10A). Also, the size of the stator coil in the axial direction increases if cooling structures are provided at both sides of a coil plate in order to enhance the cooling performance (see FIG. 10B).